The present invention relates to a method for continuous treatment of a textile product web with steam for fixing a reactive dye on natural fibers.
It also relates to a device for continuous treatment of textile product web of this type.
For fixing of reactive dyes on natural fibers, such as cotton or cellulose, it is known to first dry the moist product web on which the reactive dye is applied, and subsequently to fix the reactive dye on the fibers of the product web. For this purpose a promoter, for example urea, is needed and admixed to the reactive dye. The promoter holds the reactive dye in solution during dyeing and evaporates during fixing. This is true both for application of reactive dye on the product web by dyeing and also by printing.
For fixing of the reactive dye applied by printing, it is known to treat the dried product web with saturated steam. A suitable device with a steam chamber is disclosed in the patent document EP 0607 762B. For reduction of the urea consumption, this device is provided with a premoisturizing chamber.
A reduction of the urea quantity is possible, as described in the German patent document DE 43 03 129 02, in that the printed and dried product is sprayed with water immediately before its entry in the rapid festoon ager. This fixing process in the rapid festoon ager requires an average steam treatment time of 10-15 minutes. The product size generally amounts to 80-490 m, whereby a product speed of 5 to 50 in/mm results. In the rapid festoon ager the fixing of the reactive dye is performed conventionally with saturated steam at substantially atmospheric pressure, or in other words in saturated steam atmosphere. Rapid festoon ager for a product size of at least 80 meter is not efficient for smaller product sizes (smaller meter lengths).
A further appropriate steamer is disclosed in the German patent document DE 23 10 195 02. This steamer has a treatment chamber and a transporting device with at least partially horizontal product guidance by means of a conveyor. The treatment chamber is formed as a downwardly open hood. Thereby the entrained air can fall from a downwardly open steam space, so that a pure steam atmosphere is always available. Fixing of a drying product web in this steam atmosphere, in which a purely saturated steam atmosphere is also provided, is not possible without urea. The disadvantage of this steamer is that, due to the above mentioned steam treatment time of 10 to 15 min with saturated steam atmosphere in continuous operation, only small product speeds can be reached. Higher product speeds are possible only with greater structural length of the steamer with correspondingly higher investments and operation costs. The steam also is not efficiently usable when smaller quantities are to be dyed.
A further disadvantage of the above mentioned method is that the product web after application of reactive dye soluble in water is first dried and subsequently the reactive dye is fixed on the fibers. The both treatment stages of drying and fixing require two treatment devices. During pressing, conventionally for drying a pressing chamber and for fixing the above mentioned steam device are utilized.
In a special pressing method which is disclosed in the German patent document DE 196 33 101 the product web is moisturized, wet pressed and in wet condition evaporated without intermediate drying. The steaming is performed in a saturated steam atmosphere during 1.0-20 min at 96-105° C. Also, in this method during use of a reactive dye for printing of cotton, urea in conventional quantity is utilized.
A further special pressing method in which the product web is first moisturized, the wet product web is printed and subsequently an evaporation-thermosol fixation process is performed, it is disclosed in the patent document WO96/28604. The evaporation-thermosol fixation process takes place with saturated steam at temperatures of 90, 150 and 170° C. It requires a pressure-tight fixing device which conventionally is suitable only for a discontinuous operation.